The decline in production was the country's biggest since 2004, Chamber of Mines President Eric Asubonteng said.
Gold production by Ghana's large-scale mines fell 4.8% to 2.8 million ounces in 2020, while the small-scale gold sector was more heavily impacted as the pandemic disrupted supply chains.
Small-scale gold production fell 26% to 1.18 million ounces.
A government-mandated closure of Ghana Manganese Co caused manganese production to fall to 2.35 million tonnes in 2020 from 5.38 million in 2019.
The mining sector's share of Ghana's GDP fell to 7.5% in the year from 8.6% the year before, Asubonteng said. However the mining and quarries sector remained the leading source of direct domestic revenue, contributing 4.17 billion Ghanaian cedis ($724 million) thanks to higher gold prices boosting royalties.
($1 = 5.7600 Ghanian cedi)
(Reporting by Christian Akorlie and Helen ReidEditing by Bate Felix and David Holmes)